Transition metal complex and light-emitting device

ABSTRACT

A light-emitting device comprising a pair of electrodes and one or more organic layers disposed between the electrodes, the one or more organic layers comprising a light-emitting layer. At least one of the organic layers comprises a transition metal complex containing a moiety represented by the following formula (1): 
                 
 
wherein M 11  represents a transition metal ion; and R 11 , R 12 , R 13 , R 14 , R 15 , R 16  and R 17  represent a substituent or a single bond, respectively, or a tautomer thereof.

FIELD OF THE INVENTION

The present invention relates to a light-emitting device that convertselectric energy into light to be useful for indicating elements, displaydevices, backlights, electro-photographies, illumination light sources,recording light sources, exposing light sources, reading light sources,road signs or markings, signboards, interiors, optical communications,etc. The present invention further relates to an iridium complex usablefor the light-emitting device.

BACKGROUND OF THE INVENTION

Recently, various display devices have been widely studied. Inparticular, organic electroluminescence (EL) devices are advantageous inthat they can emit light with high luminance by a lowered applyingvoltage, whereby much attention has been paid thereto. For example, alight-emitting device comprising organic thin layers provided byvapor-depositing organic compounds has been disclosed in Applied PhysicsLetters, 51, 913 (1987). This light-emitting device has a structurewhere an electron-transporting material of tris(8-hydroxyquinolinato)aluminum complex (Alq) and a hole-transporting material of an aminecompound are disposed between electrodes as a laminate, therebyexhibiting more excellent light-emitting properties than that ofconventional light-emitting devices having a single-layer structure.

A green light-emitting device disclosed in Applied Physics Letters, 75,4 (1999) utilizes a particular ortho-metalated iridium complex, Ir(ppy)₃(Tris-Ortho-Metalated Complex of Iridium (III) with 2-Phenylpyridine),as a light-emitting material to improve light-emitting properties.Although the green light-emitting device exhibits a high externalquantum efficiency of approximately 8%, which exceeds that ofconventional light-emitting devices, 5%, it has been required to furtherimprove the device with respect to luminance, light-emitting efficiencyand durability.

Above-mentioned light-emitting device using Ir(Ppy)₃ emits only a greenlight to have a narrow applicability as a display device. Thus,expectations have been high for the development of a light-emittingdevice that can emit light of the other color with high efficiency.Turning to blue light-emitting devices, though many devices using adistyrylarylene or a derivative thereof such as DPVBi(4,4′-bis(2,2′-diphenylvinyl)-biphenyl) have been proposed, an upperlimit of external quantum efficiency has been 5%. Development of a bluelight-emitting device exhibiting the external quantum efficiencyexceeding 5% has been highly expected because it will contribute for theprogress of a color organic EL device and a white light-emitting deviceexcellent in the efficiency.

OBJECT AND SUMMARY OF THE INVENTION

An object of the present invention is to provide a light-emitting deviceexcellent in luminance, light-emitting efficiency and durability thatcan emit a light of blue, white, etc. Another object of the presentinvention is to provide a transition metal complex that is usable forthe light-emitting device and has a wide applicability for medicaltreatments, fluorescent whitening agents, photographic materials, lightabsorbing materials, laser dyes, dyes for color filters, colorconversion filters, etc.

As a result of intense research in view of the above objects, theinventor has found that a light-emitting device using a transition metalcomplex with a particular structure can emit light of blue, white, etc.with excellent luminance, light-emitting efficiency and durability. Thepresent invention has been accomplished by the finding.

Thus, a light-emitting device of the present invention comprises a pairof electrodes and one or more organic layers disposed between theelectrodes, the one or more organic layers comprising a light-emittinglayer, wherein at least one of the one or more organic layers comprisesa transition metal complex containing a moiety represented by thefollowing formula (1) or a tautomer thereof.

In the formula (1), M¹¹ represents a transition metal ion; and R¹¹, R¹²,R¹³, R¹⁴, R¹⁵, R¹⁶ and R¹⁷ represent a substituent or a single bond,respectively.

The transition metal complex preferably contains a moiety represented byany one of the following formulae (2), (8), (9), (10) and (18). Further,the transition metal complex containing the moiety of the formula (2) ispreferably represented by the following formula (3).

In the formula (2), M²¹ represents a transition metal ion; Y²¹represents a nitrogen atom or a substituted or unsubstituted carbonatom; and Q²¹ and Q²² represent an atomic group forming anitrogen-containing heterocyclic ring, respectively.

In the formula (3), M³¹ represents a transition metal ion; Y³¹represents a nitrogen atom or a substituted or unsubstituted carbonatom; Q³¹ and Q³² represent an atomic group forming anitrogen-containing heterocyclic ring, respectively; L³¹ represents aligand; X³¹ represents a counter ion; m31 represents an integer of 1 to4; m32 represents an integer of 0 to 3; and m33 represents an integer of0 to 4.

In the formula (8), M⁸¹ represents a transition metal ion; Q⁸¹represents an atomic group forming a nitrogen-containing heterocyclicring; and R⁸¹ and R⁸² represent a hydrogen atom or a substituent,respectively.

In the formula (9), M⁹¹ represents a transition metal ion; Q⁹¹ and Q⁹²represent an atomic group forming a nitrogen-containing heterocyclicring, respectively; EWG⁹¹ represents an electron-withdrawing group; andn91 represents an integer of 1 or more.

In the formula (10), M¹⁰¹ represents a transition metal ion; Q¹⁰¹represents an atomic group forming a nitrogen-containing heterocyclicring; and R¹⁰¹, R¹⁰² and R¹⁰³ represent a hydrogen atom or asubstituent, respectively.

In the formula (18), M⁸⁰¹ represents a transition metal ion; Q⁸⁰¹represents an atomic group forming a nitrogen-containing heterocyclicring; and R⁸⁰¹ represents a hydrogen atom or a substituent.

Also, the transition metal complex preferably contains a moietyrepresented by the following formula (11), more preferably contains amoiety represented by the following formula (12).

In the formula (11), M¹¹¹ represents a transition metal ion; Q¹¹¹represents an atomic group forming a ring; Q¹¹² represents an atomicgroup forming a nitrogen-containing heterocyclic ring; EWG¹¹¹ representsan electron-withdrawing group; n111 represents an integer of 1 or more;and R¹¹¹, R¹¹², R¹¹³, R¹¹⁴, R¹¹⁵, R¹¹⁶ and R¹¹⁷ represent a substituentor a single bond, respectively.

In the formula (12), R²⁰¹, R²⁰², R²⁰³, R²⁰⁴, R²⁰⁵, R²⁰⁶, R²⁰⁷ and R²⁰⁸represent a hydrogen atom or a substituent, respectively, at least oneof R²⁰¹, R²⁰², R²⁰³ and R²⁰⁴ being a fluorine atom; R²¹¹, R²¹², R²¹³,R²¹⁴, R²¹⁵, R²¹⁶ and R²¹⁷ represent a substituent or a single bond,respectively; and n131 and n132 are 1 or 2, respectively.

In the light-emitting device of the present invention, it is preferablethat the light-emitting layer comprises the transition metal complex orthe tautomer thereof and a host compound. T₁ level of the host compoundis preferably 260 to 356 kJ/mol. Further, it is preferred that acompound contained in a layer adjacent to the light-emitting layer has aT₁ level of 260 to 356 kJ/mol.

Novel transition metal complexes represented by any of the followingformulae (6), (13), (14), (19) and (20) may be preferably used for thelight-emitting device of the present invention.

In the formula (6), R⁶¹ and R⁶² represent a hydrogen atom or asubstituent, respectively; R⁶³, R⁶⁴ and R⁶⁵ represent a substituent,respectively; and n61, n62 and n63 represent an integer of 0 to 4,respectively.

In the formula (13), R³⁰¹, R³⁰², R³⁰³, R³⁰⁴, R³⁰⁵, R³⁰⁶, R³⁰⁷, R³⁰⁸,R³¹¹, R³¹², R³¹³, R³¹⁴, R³¹⁵ and R³¹⁶ represent a hydrogen atom or asubstituent, respectively.

In the formula (14), R⁴⁰¹, R⁴⁰², R⁴⁰³, R⁴⁰⁴, R⁴⁰⁵, R⁴⁰⁶, R⁴⁰⁷, R⁴⁰⁸,R⁴¹¹, R⁴¹², R⁴¹³, R⁴¹⁴, R⁴¹⁵, R⁴¹⁶ and R⁴¹⁷ represent a hydrogen atom ora substituent, respectively.

In the formula (19), R⁹⁰¹, R⁹⁰², R⁹⁰³, R⁹⁰⁴, R⁹⁰⁵, R⁹⁰⁶, R⁹⁰⁷, R⁹⁰⁸,R⁹¹², R⁹¹³, R⁹¹⁴, R⁹¹⁵ and R⁹¹⁶ represent a hydrogen atom or asubstituent, respectively. Incidentally, R⁹⁰¹, R⁹⁰², R⁹⁰³, R⁹⁰⁴, R⁹⁰⁵,R⁹⁰⁶, R⁹⁰⁷, R⁹⁰⁸, R⁹¹², R⁹¹³, R⁹¹⁴, R⁹¹⁵ and R⁹¹⁶ are free of atransition metal ion or a transition metal atom.

In the formula (20), Y⁹²¹ and Y⁹²² represent a nitrogen atom or asubstituted or unsubstituted carbon atom, respectively; and R⁹²², R⁹²³,R⁹²⁴, R⁹²⁵ and R⁹²⁶ represent a hydrogen atom or a substituent,respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[1] Transition Metal Complex

A light-emitting device of the present invention comprises a transitionmetal complex containing a moiety represented by the following formula(1) or a tautomer thereof. In the present invention, the transitionmetal complex containing the moiety represented by the formula (1) andthe tautomer thereof is hereinafter referred to as “transition metalcomplex (1)”.

In the formula (1), M¹¹ represents a transition metal ion. Thetransition metal ion is not particularly limited, preferably a rutheniumion, a rhodium ion, a palladium ion, a tungsten ion, a rhenium ion, anosmium ion, an iridium ion or a platinum ion, more preferably aruthenium ion, a rhenium ion, an iridium ion or a platinum ion,particularly preferably an iridium ion, most preferably a trivalentiridium ion.

R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶ and R¹⁷ represent a substituent or a singlebond, respectively. R¹² and R¹³ may form a carbon-carbon double bond, acarbon-oxygen double bond or a carbon-nitrogen double bond incombination with each other. Also, R¹⁴ and R¹⁵ may form a carbon-carbondouble bond, a carbon-oxygen double bond or a carbon-nitrogen doublebond in combination with each other. Further, combination of R¹⁵ and R¹⁶may form a carbon-nitrogen double bond, and combination of R¹⁶ and R¹⁷may form a carbon-nitrogen double bond or a nitrogen-nitrogen doublebond.

Examples of the substituent represented by R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶or R¹⁷ include: alkyl groups, the number of carbon atom thereof beingpreferably 1 to 30, more preferably 1 to 20, particularly preferably 1to 10, such as a methyl group, an ethyl group, an isopropyl group, at-butyl group, a n-octyl group, a n-decyl group, a n-hexadecyl group, acyclopropyl group, a cyclopentyl group and a cyclohexyl group; alkenylgroups, the number of carbon atoms thereof being preferably 2 to 30,more preferably 2 to 20, particularly preferably 2 to 10, such as avinyl group, an allyl group, a 2-butenyl group and a 3-pentenyl group;alkynyl groups, the number of carbon atoms thereof being preferably 2 to30, more preferably 2 to 20, particularly preferably 2 to 10, such as apropargyl group and a 3-pentynyl group; aryl groups, the number ofcarbon atoms thereof being preferably 6 to 30, more preferably 6 to 20,particularly preferably 6 to 12, such as a phenyl group, ap-methylphenyl group, a naphtyl group, an anthryl group, a phenanthrylgroup and a pyrenyl group; amino groups, the number of carbon atomthereof being preferably 0 to 30, more preferably 0 to 20, particularlypreferably 0 to 10, such as a unsubstituted amino group, a methylaminogroup, a dimethylamino group, a diethylamino group, a dibenzylaminogroup, a diphenylamino group and a ditolylamino group; alkoxy groups,the number of carbon atom thereof being preferably 1 to 30, morepreferably 1 to 20, particularly preferably 1 to 10, such as a methoxygroup, an ethoxy group, a butoxy group and a 2-ethylhexyloxy group;aryloxy groups, the number of carbon atoms thereof being preferably 6 to30, more preferably 6 to 20, particularly preferably 6 to 12, such as aphenyloxy group, a 1-naphthyloxy group and a 2-naphthyloxy group;heterocyclic oxy groups, the number of carbon atom thereof beingpreferably 1 to 30, more preferably 1 to 20, particularly preferably 1to 12, such as a pyridyloxy group, a pyrazyloxy group, a pyrimidyloxygroup and a quinolyloxy group; silyloxy groups, the number of carbonatom thereof being preferably 3 to 40, more preferably 3 to 30,particularly preferably 3 to 24, such as a trimethylsilyloxy group and atriphenylsilyloxy group; acyl groups, the number of carbon atom thereofbeing preferably 1 to 30, more preferably 1 to 20, particularlypreferably 1 to 12, such as an acetyl group, a benzoyl group, a formylgroup and a pivaloyl group; alkoxycarbonyl groups, the number of carbonatoms thereof being preferably 2 to 30, more preferably 2 to 20,particularly preferably 2 to 12, such as a methoxycarbonyl group and anethoxycarbonyl group; aryloxycarbonyl groups, the number of carbon atomsthereof being preferably 7 to 30, more preferably 7 to 20, particularlypreferably 7 to 12, such as a phenyloxycarbonyl group; acyloxy groups,the number of carbon atoms thereof being preferably 2 to 30, morepreferably 2 to 20, particularly preferably 2 to 10, such as an acetoxygroup and a benzoyloxy group; acylamino groups, the number of carbonatoms thereof being preferably 2 to 30, more preferably 2 to 20,particularly preferably 2 to 10, such as an acetylamino group and abenzoylamino group; alkoxycarbonylamino groups, the number of carbonatoms thereof being preferably 2 to 30, more preferably 2 to 20,particularly preferably 2 to 12, such as a methoxycarbonylamino group;aryloxycarbonylamino groups, the number of carbon atoms thereof beingpreferably 7 to 30, more preferably 7 to 20, particularly preferably 7to 12, such as a phenyloxycarbonylamino group; sulfonylamino groups, thenumber of carbon atom thereof being preferably 1 to 30, more preferably1 to 20, particularly preferably 1 to 12, such as a methanesulfonylamino group and a benzene sulfonylamino group; sulfamoyl groups,the number of carbon atom thereof being preferably 0 to 30, morepreferably 0 to 20, particularly preferably 0 to 12, such as aunsubstituted sulfamoyl group, a methylsulfamoyl group, adimethylsulfamoyl group and a phenylsulfamoyl group; carbamoyl groups,the number of carbon atom thereof being preferably 1 to 30, morepreferably 1 to 20, particularly preferably 1 to 12, such as aunsubstituted carbamoyl group, a methylcarbamoyl group, adiethylcarbamoyl group and a phenylcarbamoyl group; alkylthio groups,the number of carbon atom thereof being preferably 1 to 30, morepreferably 1 to 20, particularly preferably 1 to 12, such as amethylthio group and an ethylthio group; arylthio groups, the number ofcarbon atoms thereof being preferably 6 to 30, more preferably 6 to 20,particularly preferably 6 to 12, such as a phenylthio group;heterocyclic thio groups, the number of carbon atom thereof beingpreferably 1 to 30, more preferably 1 to 20, particularly preferably 1to 12, such as a pyridylthio group, a 2-benzimidazolylthio group, a2-benzoxazolylthio group and a 2-benzthiazolylthio group; sulfonylgroups, the number of carbon atom thereof being preferably 1 to 30, morepreferably 1 to 20, particularly preferably 1 to 12, such as a mesylgroup and a tosyl group; sulfinyl groups, the number of carbon atomthereof being preferably 1 to 30, more preferably 1 to 20, particularlypreferably 1 to 12, such as a methane sulfinyl group and a benzenesulfinyl group; ureide groups, the number of carbon atom thereof beingpreferably 1 to 30, more preferably 1 to 20, particularly preferably 1to 12, such as a unsubstituted ureide group, a methylureide group and aphenylureide group; phosphoric amide groups, the number of carbon atomthereof being preferably 1 to 30, more preferably 1 to 20, particularlypreferably 1 to 12, such as a diethylphosphoric amide group and aphenylphosphoric amide group; a hydroxyl group; a mercapto group;halogen atoms such as a fluorine atom, a chlorine atom, a bromine atomand an iodine atom; a cyano group; a sulfo group; a carboxyl group; anitro group; a hydroxamic acid group; a sulfino group; a hydrazinogroup; an imino group; heterocyclic groups that may be aliphatic oraromatic and may have a nitrogen atom, a oxygen atom, a sulfur atom,etc. as a hetero atom, the number of carbon atom thereof beingpreferably 1 to 30, more preferably 1 to 12, such as an imidazolylgroup, a pyridyl group, a quinolyl group, a furyl group, a thienylgroup, a piperidyl group, a morpholino group, a benzoxazolyl group, abenzoimidazolyl group, a benzothiazolyl group, a carbazolyl group and anazepinyl group; silyl groups, the number of carbon atom thereof beingpreferably 3 to 40, more preferably 3 to 30, particularly preferably 3to 24, such as a trimethylsilyl group and a triphenylsilyl group;phosphino groups, the number of carbon atom thereof being preferably 2to 30, more preferably 2 to 12, such as a dimethylphosphino group and adiphenylphosphino group; etc. The substituent may be furthersubstituted. When two or more of R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶ and R¹⁷each represents the substituent, they may be the same or different andmay bond together to form a ring. The substituent may bond to the metalatom to form a chelate complex.

R¹¹ is preferably an alkyl group, an alkenyl group, an aryl group, acarbonyl group, a sulfonyl group or a substituted amino group.

It is preferred that R¹² and R¹³ are an alkyl group or an aryl group,respectively, or that R¹² and R¹³ form a carbon-oxygen double bond, acarbon-nitrogen double bond or a carbon-carbon double bond incombination with each other.

It is preferred that R¹⁴ and R¹⁵ are an alkyl group or an aryl group,respectively, or that R¹⁴ and R¹⁵ form a carbon-oxygen double bond, acarbon-nitrogen double bond or a carbon-carbon double bond incombination with each other. It is also preferred that R¹⁵ forms acarbon-nitrogen double bond in combination with R¹⁶.

It is preferred that R¹⁶ and R¹⁷ are an alkyl group, an aryl group or asubstituted amino group, respectively, or that R¹⁶ and R¹⁷ form acarbon-nitrogen double bond or a nitrogen-nitrogen double bond incombination with each other. It is also preferred that R¹⁶ forms acarbon-nitrogen double bond in combination with R¹⁵.

The transition metal complex (1) may comprise one transition metal atomor a plurality of transition metal atoms, thus, the transition metalcomplex (1) may be a so-called multi-nuclear complex. In the case of themulti-nuclear complex, a plurality of transition metal atoms may be thesame or different atoms.

The transition metal complex (1) may comprise ligands of a plurality ofkinds. The transition metal complex (1) preferably comprises 1 to 3 kindof ligand, more preferably comprises 1 or 2 kind of ligand.

The transition metal complex (1) may comprise a ligand other than thatcontained in the moiety of the formula (1). Such a ligand is notparticularly limited and may be such that is disclosed in: H. Yersin,“Photochemistry and Photophysics of Coordination Compounds”,Springer-Verlag, Inc. (1987); Akio Yamamoto, “Yukikinzoku-Kagaku, Kisoto Oyo (Metalorganic Chemistry, Foundation and Application)”, ShokaboPublishing Co., Ltd., (1982); etc. Preferred as the ligand are: halogenligands such as a chlorine ligand and a fluorine ligand;nitrogen-containing heterocyclic ring ligands such as bipyridyl ligands,phenanthroline ligands and phenylpyridine ligands; diketone ligands;nitrile ligands; CO ligand; isonitrile ligands; phosphorus ligands suchas phosphine ligands, phosphite ligands and phosphinine ligands; andcarboxylic acid ligands such as an acetic acid ligand.

The transition metal complex (1) may be a neutral complex or an ioniccomplex comprising a counter ion. The counter ion is not particularlylimited. The counter ion is preferably an alkaline metal ion, analkaline earth metal ion, a halogen ion, a perchlorate ion, a PF₆ ion,an ammonium ion such as a tetramethylammonium ion, a borate ion or aphosphonium ion, more preferably a perchlorate ion or a PF₆ ion. Thetransition metal complex (1) is preferably a neutral complex.

The transition metal complex (1) is preferably a transition metalcomplex containing a moiety represented by any one of the followingformulae (2), (8), (9), (10) and (18) or a tautomer thereof, morepreferably a transition metal complex containing a moiety represented byany one of the formulae (8), (10) and (18) or a tautomer thereof,particularly preferably a transition metal complex containing a moietyrepresented by the formula (8) or a tautomer thereof.

The transition metal complex containing the moiety represented by theformula (2) or the tautomer thereof is preferably a transition metalcomplex represented by the following formula (3) or a tautomer thereof,more preferably a transition metal complex represented by the followingformula (4) or a tautomer thereof, particularly preferably a transitionmetal complex represented by the following formula (5) or a tautomerthereof. Preferred embodiments of the transition metal complexrepresented by the formula (5) include such that is represented by anyof the following formulae (6) and (7). Further, it is also preferablethat the transition metal complex containing the moiety represented bythe formula (2) is represented by the following formula (20).

The formula (2) will be described below. In the formula (2), M²¹ is thesame as above-mentioned M¹¹ with respect to meaning and preferredembodiments. Y²¹ represents a nitrogen atom or a substituted orunsubstituted carbon atom. The carbon atom may has a substituent withexamples being the same as those for the substituent represented by R¹¹to R¹⁷. Q²¹ and Q²² represent an atomic group forming anitrogen-containing heterocyclic ring, respectively.

The nitrogen-containing heterocyclic ring formed by Q²¹ is notparticularly limited and preferably an imidazole ring, a pyrrole ring, atriazole ring, a pyrazole ring, an imidazoline ring, a pyridone ring ora condensed ring thereof such as a benzimidazole ring and an indolering.

The nitrogen-containing heterocyclic ring formed by Q²² is notparticularly limited and preferably a pyridine ring, a pyrazine ring, apyrimidine ring, a triazine ring, a thiazole ring, an oxazole ring, animidazole ring, a pyrazole ring, a triazole ring, an indolenine ring ora condensed ring thereof such as a quinoline ring, a benzoxazole ringand a benzimidazole ring.

The formula (3) will be described below. In the formula (3), M³¹, Y³¹,Q³¹ and Q³² are the same as above-mentioned M²¹, Y²¹, Q²¹ and Q²² withrespect to meaning and preferred embodiments, respectively. L³¹represents a ligand, and X³¹ represents a counter ion.

The ligand represented by L³¹ may be the same as the above-mentionedligand other than that contained in the moiety of the formula (1). Theligand represented by L³¹ is preferably selected from the groupconsisting of: halogen ligands such as a chlorine ligand and a fluorineligand; nitrogen-containing heterocyclic ring ligands such asphenylpyridine ligands, benzoquinoline ligands, quinolinol ligands,bipyridyl ligands and phenanthroline ligands; diketone ligands such asacetylacetone; carboxylic acid ligands such as an acetic acid ligand, abenzoic acid ligand and a picolinic acid ligand; a carbon monoxideligand; isonitrile ligands; cyano ligands; and phosphorus ligands suchas phosphine ligands, phosphite ligands and phosphinine ligands.

The counter ion represented by X³¹ is not particularly limited, andpreferably an alkaline metal ion, an alkaline earth metal ion, a halogenion, a perchlorate ion, a PF₆ ion, an ammonium ion such as atetramethylammonium ion, a borate ion or a phosphonium ion, morepreferably a perchlorate ion or a PF₆ ion.

m31 is an integer of 1 to 4, preferably 1, 2 or 3. m32 is an integer of0 to 3, preferably 0, 1 or 2. m33 is an integer of 0 to 4, preferably 0,1 or 2, more preferably 0. When m32 is 2 or more, a plurality of L³¹'smay be the same or different ligands. When m33 is 2 or more, a pluralityof X³¹'s may be the same or different counter ions. m31 and m32 areparticularly preferably selected such that the transition metal complex(1) is a neutral complex.

The formula (4) will be described below. In the formula (4), M⁴¹, Q⁴²,X⁴¹, L⁴¹, m41, m42 and m43 are the same as above-mentioned M³¹, Q³²,X³¹, L³¹, m31, m32 and m33 with respect to meaning and preferredembodiments, respectively. R⁴¹ and R⁴² represent a hydrogen atom or asubstituent with examples being the same as those for the substituentrepresented by R¹¹ to R¹⁷, respectively. R⁴¹ and R⁴² may bond togetherto form a condensed ring structure such as a benzimidazole ring. It ispreferable that R⁴¹ and R⁴² are a hydrogen atom, an alkyl group or anaryl group, respectively, or that R⁴¹ and R⁴² bond together to form anaromatic ring. It is more preferable that R⁴¹ and R⁴² are an alkyl groupor an aryl group, respectively, or that R⁴¹ and R⁴² bond together toform an aromatic ring.

The formula (5) will be described below. In the formula (5), M⁵¹, L⁵¹,R⁵¹, R⁵², m51 and m52 are the same as above-mentioned M⁴¹, L⁴¹, R⁴¹,R⁴², m41 and m42 with respect to meaning and preferred embodiments,respectively. Y⁵¹, Y⁵², Y⁵³ and Y⁵⁴ represent a substituted orunsubstituted carbon atom or a nitrogen atom, respectively. The carbonatom may have a substituent with examples being the same as those forthe substituent represented by R¹¹ to R¹⁷.

The formula (6) will be described below. In the formula (6), R⁶¹ and R⁶²are the same as above-mentioned R⁵¹ and R⁵² with respect to meaning andpreferred embodiments, respectively. R⁶³, R⁶⁴ and R⁶⁵ represent asubstituent with examples being the same as those for the substituentrepresented by R¹¹ to R¹⁷, respectively. R⁶³, R⁶⁴ and R⁶⁵ are preferablyan alkyl group, an aryl group, an alkoxy group, a substituted aminogroup or a halogen atom, more preferably an alkyl group, an aryl groupor a fluorine atom, respectively. n61, n62 and n63 are an integer of 0to 4, preferably 0, 1 or 2, respectively.

The formula (7) will be described below. In the formula (7), M⁷¹, R⁷¹,R⁷², R⁷³, m71, m72 and n71 are the same as above-mentioned M⁵¹, R⁵¹,R⁵², R⁶³, m51, m52 and n61 with respect to meaning and preferredembodiments, respectively. R⁷⁷, R⁷⁸ and R⁷⁹ represent a hydrogen atom ora substituent with examples being the same as those for the substituentrepresented by R¹¹ to R¹⁷, respectively. R⁷⁷ and R⁷⁹ are preferably analkyl group, an aryl group, an alkoxy group or an amino group, morepreferably an alkyl group, respectively. R⁷⁸ is preferably a hydrogenatom, an alkyl group or an aryl group, more preferably a hydrogen atomor an alkyl group.

The formula (20) will be described below. In the formula (20), R⁹²²,R⁹²³, R⁹²⁴, R⁹²⁵ and R⁹²⁶ represent a hydrogen atom or a substituentwith examples being the same as those for the substituent represented byR¹¹ to R¹⁷, respectively. R⁹²² is preferably a hydrogen atom, an alkylgroup, an aryl group or an electron-withdrawing group. Hammett sigmaconstant (σp or σm, reference: Chem. Rev. 1991, 91, 165) of thiselectron-withdrawing group is preferably 0.1 or more, more preferably0.3 or more. Preferred as the electron-withdrawing group are a fluorineatom, a trifluoromethyl group, an acetyl group, a methane sulfonylgroup, a trifluoroacetyl group, a trifluoromethane sulfonyl group and acyano group. Among them, more preferred are a fluorine atom, atrifluoromethyl group, a trifluoroacetyl group and a trifluoromethanesulfonyl group, and further preferred are a fluorine atom and atrifluoromethyl group, particularly preferred is a trifluoromethylgroup.

Y⁹²¹ and Y⁹²² represent a nitrogen atom or a substituted orunsubstituted carbon atom, respectively. The carbon atom may have asubstituent with examples being the same as those for the substituentrepresented by R¹¹ to R¹⁷. The substituent on the carbon atom haspreferred embodiments as above-mentioned R⁹²². Y⁹²¹ is preferably asubstituted or unsubstituted carbon atom, and Y⁹²² is preferably anitrogen atom.

The transition metal complex containing the moiety represented by thefollowing formula (8) or the tautomer thereof is preferably a transitionmetal complex represented by the following formula (15) or a tautomerthereof, more preferably a transition metal complex represented by thefollowing formula (13) or a tautomer thereof.

The formula (8) will be described below. In the formula (8), M⁸¹ and Q⁸¹are the same as above-mentioned M¹¹ and Q³² with respect to meaning andpreferred embodiments, respectively. R⁸¹ and R⁸² represent a hydrogenatom or a substituent with examples being the same as those for thesubstituent represented by R¹¹ to R¹⁷, respectively. R⁸¹ and R⁸² arepreferably a hydrogen atom, an alkyl group, an aryl group or anelectron-withdrawing group, respectively. It is particularly preferablethat at least one of R⁸¹ and R⁸² is an electron-withdrawing group. Thiselectron-withdrawing group has the same preferred embodiments asdescribed for that represented by R⁹²² in the formula (20).

The formula (15) will be described below. In the formula (15), M⁵⁰¹,Q⁵⁰¹, X⁵⁰¹, L⁵⁰¹, m501, m502, m503, R⁵¹¹ and R⁵¹² are the same asabove-mentioned M⁸¹, Q⁸¹, X³¹, L³¹, m31, m32, m33, R⁸¹ and R⁸² withrespect to meaning and preferred embodiments, respectively.

The formula (13) will be described below. In the formula (13), R³⁰¹,R³⁰², R³⁰³ and R³⁰⁴ represent a hydrogen atom or a substituent,respectively. R³⁰¹ and R³⁰³ are preferably a hydrogen atom, an alkylgroup or a fluorine atom, more preferably a hydrogen atom, respectively.R³⁰² is preferably a hydrogen atom, an alkyl group or a fluorine atom,more preferably a fluorine atom. R³⁰⁴ is preferably a hydrogen atom, analkyl group or a fluorine atom, more preferably a hydrogen atom or afluorine atom, particularly preferably a fluorine atom. R³⁰⁵, R³⁰⁶, R³⁰⁷and R³⁰⁸ represent a hydrogen atom or a substituent, respectively. R³⁰⁵and R³⁰⁷ are preferably a hydrogen atom, an alkyl group or an alkoxygroup, more preferably a hydrogen atom or an alkyl group, respectively.R³⁰⁶ and R³⁰⁸ are preferably a hydrogen atom, an alkyl group, an alkoxygroup or a dialkylamino group, more preferably a hydrogen atom, an alkylgroup or an alkoxy group, particularly preferably an alkoxy group,respectively. R³¹¹ and R³¹² are the same as above-mentioned R⁸¹ and R⁸²with respect to meaning and preferred embodiments, respectively. R³¹³,R³¹⁴, R³¹⁵ and R³¹⁶ are the same as above-mentioned R³⁰⁵, R³⁰⁶, R³⁰⁷ andR³⁰⁸ with respect to meaning and preferred embodiments, respectively.

The transition metal complex containing the moiety represented by thefollowing formula (9) or the tautomer thereof is preferably a transitionmetal complex represented by the following formula (16) or a tautomerthereof.

The formula (9) will be described below. In the formula (9), M⁹¹ and Q⁹¹are the same as above-mentioned M¹¹ and Q³² with respect to meaning andpreferred embodiments, respectively. Q⁹² represents an atomic groupforming a nitrogen-containing heterocyclic ring. The nitrogen-containingheterocyclic ring formed by Q⁹² is preferably a pyrrole ring, animidazole ring, a pyrazole ring, a triazole ring, a benzimidazole ringor an indole ring, more preferably a pyrrole ring, a pyrazole ring or animidazole ring, particularly preferably a pyrazole ring. EWG⁹¹represents an electron-withdrawing group having the same preferredembodiments as described for that represented by R⁹²² in the formula(20). n91 is an integer of 1 or more, preferably an integer of 1 to 3,more preferably 1 or 2.

The formula (16) will be described below. In the formula (16), Y⁶⁰¹,Y⁶⁰² and Y⁶⁰³ represent a nitrogen atom or a substituted orunsubstituted carbon atom, respectively, at least one of Y⁶⁰¹, Y⁶⁰² andY⁶⁰³ being a carbon atom substituted by an electron-withdrawing group.This electron-withdrawing group has the same preferred embodiments asdescribed for that represented by R⁹²² in the formula (20). Q⁶⁰¹, X⁶⁰¹,L⁶⁰¹, m601, m602 and m603 are the same as above-mentioned Q⁹¹, X³¹, L³¹,m31, m32 and m33 with respect to meaning and preferred embodiments,respectively.

The transition metal complex containing the moiety represented by thefollowing formula (10) or the tautomer thereof is preferably atransition metal complex represented by the following formula (17) or atautomer thereof, more preferably a transition metal complex representedby the following formula (14) or a tautomer thereof.

The formula (10) will be described below. In the formula (10), M¹⁰¹ andQ¹⁰¹ are the same as above-mentioned M¹¹ and Q³² with respect to meaningand preferred embodiments, respectively. R¹⁰¹, R¹⁰² and R¹⁰³ represent ahydrogen atom or a substituent, respectively. R¹⁰¹ and R¹⁰² arepreferably a hydrogen atom or an alkyl group, respectively. R¹⁰³ ispreferably an electron-withdrawing group, more preferably a substitutedcarbonyl group (an acetyl group, a dialkylaminocarbonyl group, amethoxycarbonyl group, a perfluorophenylcarbonyl group, etc.), asubstituted sulfonyl group (a methane sulfonyl group, a benzene sulfonylgroup, etc.), a substituted sulfoxide group (a methylsulfoxide group,etc.) or a trifluoromethyl group, further preferably an acyl group (anacetyl group, a trifluoromethyl group, a perfluorobenzoyl group, etc.)or a substituted sulfonyl group, particularly preferably afluorine-substituted acyl group, a fluorine-substituted alkylsulfonylgroup or a fluorine-substituted arylsulfonyl group.

The formula (17) will be described below. In the formula (17), M⁷⁰¹,X⁷⁰¹, L⁷⁰¹, m701, m702 and m703 are the same as above-mentioned M¹⁰¹,X³¹, L³¹, m31, m32 and m33 with respect to meaning and preferredembodiments, respectively. R⁷¹¹ is the same as above-mentioned R¹⁰³ withrespect to meaning and preferred embodiments. R⁷¹² and R⁷¹³ are the sameas above-mentioned R¹⁰¹ and R¹⁰² with respect to meaning and preferredembodiments, respectively. R⁷¹⁴, R⁷¹⁵, R⁷¹⁶ and R⁷¹⁷ are the same asabove-mentioned R³¹³, R³¹⁴, R³¹⁵ and R³¹⁶ with respect to meaning andpreferred embodiments, respectively.

The formula (14) will be described below. In the formula (14), R⁴⁰¹,R⁴⁰², R⁴⁰³, R⁴⁰⁴, R⁴⁰⁵, R⁴⁰⁶, R⁴⁰⁷ and R⁴⁰⁸ are the same asabove-mentioned R³⁰¹, R³⁰², R³⁰³, R³⁰⁴, R³⁰⁵, R³⁰⁶, R³⁰⁷ and R³⁰⁸ withrespect to meaning and preferred embodiments, respectively. R⁴¹¹, R⁴¹²,R⁴¹³, R⁴¹⁴, R⁴¹⁵, R⁴¹⁶and R⁴¹⁷ are the same as above-mentioned R⁷¹¹,R⁷¹², R⁷¹³, R⁷¹⁴, R⁷¹⁵, R⁷¹⁶ and R⁷¹⁷ with respect to meaning andpreferred embodiments, respectively.

The transition metal complex containing the moiety represented by thefollowing formula (18) or the tautomer thereof is preferably atransition metal complex represented by the following formula (19) or atautomer thereof.

The formula (18) will be described below. In the formula (18), M⁸⁰¹,Q⁸⁰¹ and R⁸⁰¹ are the same as above-mentioned M¹¹, Q³² and R⁸² withrespect to meaning and preferred embodiments, respectively.

The formula (19) will be described below. In the formula (19), R⁹⁰¹,R⁹⁰², R⁹⁰³, R⁹⁰⁴, R⁹⁰⁵, R⁹⁰⁶, R⁹⁰⁷, R⁹⁰⁸, R⁹¹², R⁹¹³, R⁹¹⁴, R⁹¹⁵ andR⁹¹⁶ are the same as above-mentioned R³⁰¹, R³⁰², R³⁰³, R³⁰⁴, R³⁰⁵, R³⁰⁶,R³⁰⁷, R³⁰⁸, R³¹², R³¹³, R³¹⁴, R³¹⁵ and R³¹⁶ with respect to meaning andpreferred embodiments, respectively. Incidentally, R⁹⁰¹, R⁹⁰², R⁹⁰³,R⁹⁰⁴, R⁹⁰⁵, R⁹⁰⁶, R⁹⁰⁷, R⁹⁰⁸, R⁹¹², R⁹¹³, R⁹¹⁴, R⁹¹⁵ and R⁹¹⁶ preferablycontain no transition metal ion and no transition metal atom.

Further, the transition metal complex (1) is preferably a transitionmetal complex containing a moiety represented by the following formula(11) or a tautomer thereof, more preferably a transition metal complexcontaining a moiety represented by the following formula (12) or atautomer thereof.

The formula (11) will be described below. In the formula (11), M¹¹¹ andQ¹¹² are the same as above-mentioned M¹¹ and Q³² with respect to meaningand preferred embodiments, respectively. Q¹¹¹ represents an atomic groupforming a ring. The ring formed by Q¹¹¹ may be: an aromatic hydrocarbonring such as a benzene ring and a naphthalene ring; an aromaticheterocycle such as a pyridine ring, a pyrazine ring, a quinoline ring,a furan ring and a thiophene ring; an aliphatic hydrocarbon ring such asa cyclohexene ring; aliphatic heterocycle such as a pyrane ring; etc. Ofthese, preferred are a benzene ring, a pyridine ring, a pyrazine ringand a pyrimidine ring, more preferred is a benzene ring. EWG¹¹¹represents an electron-withdrawing group with the same examples asdescribed for that represented by R⁸¹ and R⁸² in the formula (8). EWG¹¹¹is preferably a fluorine atom. n111 is an integer of 1 or more,preferably an integer of 1 to 4, more preferably 1 or 2. R¹¹¹, R¹¹²,R¹¹³, R¹¹⁴, R¹¹⁵, R¹¹⁶ and R¹¹⁷ are the same as above-mentioned R¹¹,R¹², R¹³, R¹⁴, R¹⁵, R¹⁶ and R¹⁷ with respect to meaning and preferredembodiments, respectively.

The formula (12) will be described below. In the formula (12), R²⁰¹,R²⁰², R²⁰³, R²⁰⁴, R²⁰⁵, R²⁰⁶, R²⁰⁷ and R²⁰⁸ are the same asabove-mentioned R³⁰¹, R³⁰², R³⁰³, R³⁰⁴, R³⁰⁵, R³⁰⁶, R³⁰⁷ and R³⁰⁸ withrespect to meaning and preferred embodiments, respectively.Incidentally, at least one of R²⁰¹, R²⁰², R²⁰³ and R²⁰⁴ is a fluorineatom. R²¹¹, R²¹², R²¹³, R²¹⁴, R²¹⁵, R²¹⁶ and R²¹⁷ are the same asabove-mentioned R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶ and R¹⁷ with respect tomeaning and preferred embodiments, respectively. n131 and n132 are 1 or2, respectively. n131 is preferably 2 and n132 is preferably 1.

The transition metal complex (1) is preferably a low molecular weightcompound though it may be an oligomer or a polymer having a main chainor a side chain of repeating units containing the moiety represented bythe formula (1). In the case where the transition metal complex (1) isan oligomer or a polymer, its weight-average molecular weight determinedby polystyrene standard is preferably 1,000 to 5,000,000, morepreferably 2,000 to 1,000,000, particularly preferably 3,000 to 100,000.

The transition metal complex (1) may be such that acts as ahole-injecting material, a hole-transporting material, a light-emittingmaterial, an electron-transporting material, an electron-injectingmaterial, etc. The transition metal complex (1) may have a plurality offunctions. In this invention, the transition metal complex (1) ispreferably used as a light-emitting material or an electron-transportingmaterial, more preferably used as a light-emitting material. In the caseof using the transition metal complex (1) as the light-emittingmaterial, the maximum emission wavelength λ_(max) of the transitionmetal complex (1) is preferably 380 nm to 500 nm, more preferably 400 nmto 480 nm. Concrete examples of the transition metal complex (1) will beillustrated below without intention of restricting the scope of thepresent invention defined by the claims attached hereto.

The transition metal complex (1) can be synthesized by various methods,for example, it may be prepared by mixing a ligand or a dissociationderivative thereof with a transition metal compound under a condition ofheating or room temperature or less. Heating may be achieved by ageneral method, microwave, etc. A solvent (a halogenated solvent, analcohol solvent, an ether solvent, water, etc.) and/or an inorganic ororganic base (sodium methoxide, potassium t-butoxide, triethylamine,potassium carbonate, etc.) may be used for synthesis of the transitionmetal complex (1).

[2] Light-Emitting Device

A light-emitting device of the present invention comprises a pair ofelectrodes (positive electrode and negative electrode) and one or moreorganic layers including a light-emitting layer disposed between theelectrodes. At least one of the organic layers comprises theabove-mentioned transition metal complex (1). Although system utilizingthe light-emitting device, a driving method therefor, use thereof, etc.are not particularly limited, the light-emitting device is preferablysuch that using the transition metal complex (1) as a light-emittingmaterial or an electron-transporting material, more preferably such thatusing the transition metal complex (1) as a light-emitting material. Anorganic electroluminescence (EL) device is known as a typicallight-emitting device.

In the light-emitting device of the present invention, it is preferablethat the light-emitting layer comprises a host compound doped with thetransition metal complex (1) acting as a guest compound. It is preferredthat T₁ level of the host compound is larger than that of the guestcompound, wherein “T₁ level” means an energy level at a lowest tripletexcited state. The T₁ level of the host compound is preferably 260 to356 kJ/mol (62 to 85 kcal/mol), more preferably 272 to 335 kJ/mol (65 to80 kcal/mol).

It is preferred that T₁ level of a compound contained in a layer such asa hole-transporting layer, an electron-transporting layer, ahole-blocking layer, etc. adjacent to the light-emitting layer is largerthan that of the guest compound contained in the light-emitting layer.The T₁ level of the compound contained in the layer adjacent to thelight-emitting layer is preferably 260 to 356 kJ/mol (62 to 85kcal/mol), more preferably 272 to 335 kJ/mol (65 to 80 kcal/mol). As thecompound having such a T₁ level, compounds disclosed in Japanese PatentApplication Nos. 2001-197135 and 2001-76704 are preferably used.Preferred embodiments of the compound are described in Japanese PatentApplication Nos. 2001-197135 and 2001-76704.

Method for providing the organic layer comprising the transition metalcomplex (1) is not particularly limited, and the organic layer may beprovided by a resistance heating vapor deposition method, an electronbeam method, a sputtering method, a molecular stacking method, a coatingmethod, an ink-jet method, a printing method, a transferring method,etc. Among the methods, preferred are the resistance heating vapordeposition method and the coating method from the viewpoints ofsimplification of production processes and properties of thelight-emitting device.

The light-emitting device of the present invention may comprise ahole-injecting layer, a hole-transporting layer, an electron-injectinglayer, an electron-transporting layer, a protective layer, etc. as theorganic layer in addition to the light-emitting layer. These layers mayhave a plurality of functions. Although the transition metal complex (1)may be contained in any of the layers, the transition metal complex (1)is preferably used for the light-emitting layer or thecharge-transporting layer, more preferably used for the light-emittinglayer. Each component of the light-emitting device according to thepresent invention will be described in detail below.

(A) Positive Electrode

The positive electrode acts to supply holes to the hole-injecting layer,the hole-transporting layer, the light-emitting layer, etc. The positiveelectrode is made of a metal, an alloy, a metal oxide, an electricallyconductive compound, a mixture thereof, etc., preferably made of amaterial having a work function of 4.0 eV or more. Examples of amaterial for the positive electrode include: metals such as gold,silver, chromium and nickel; electrically conductive metal oxides suchas tin oxide, zinc oxide, indium oxide and ITO (Indium Tin Oxide);mixtures and laminations of the metal and the electrically conductivemetal oxide; electrically conductive inorganic compounds such as copperiodide and copper sulfide; electrically conductive organic compoundssuch as polyaniline, polythiophene and polypyrrole; laminations of theelectrically conductive organic compound and ITO; etc. Among thematerials, preferred are the electrically conductive metal oxides,particularly preferred is ITO from the viewpoints of productivity,electroconductivity, transparency, etc.

Method for providing the positive electrode may be selected depending onthe material used therefor. For example, the positive electrode made ofITO may be formed by an electron beam method, a sputtering method, aresistance heating vapor deposition method, a chemical reaction methodsuch as a sol-gel method, a coating method using a dispersion containingindium tin oxide, etc. The positive electrode may be subjected to awashing treatment, etc., to lower the driving voltage, or to increasethe light-emitting efficiency of the light-emitting device. For example,in the case of the positive electrode made of ITO, UV-ozone treatmentand plasma treatment are effective. Sheet resistance of the positiveelectrode is preferably a few hundred Ω/square or less. Althoughthickness of the positive electrode may be appropriately selecteddepending on the material used therefor, generally, the thickness ispreferably 10 nm to 5 μm, more preferably 50 m to 1 μm, particularlypreferably 100 to 500 nm.

The positive electrode is generally disposed on a substrate made of asoda lime glass, a non-alkali glass, a transparent resin, etc. The glasssubstrate is preferably made of the non-alkali glass to reduce ionelution. In the case of using the soda lime glass, it is preferred thatthe substrate is coated with silica, etc. beforehand. Thickness of thesubstrate is not particularly limited if only it has sufficientstrength. In the case of the glass substrate, the thickness is generally0.2 mm or more, preferably 0.7 mm or more.

(B) Negative Electrode

The negative electrode acts to supply electrons to theelectron-injecting layer, the electron-transporting layer, thelight-emitting layer, etc. Material for the negative electrode may beselected from metals, alloys, metal halides, metal oxides, electricallyconductive compounds, mixtures thereof, etc. correspondingly toionization potential, stability, adhesion property with a layer adjacentto the negative electrode such as the light-emitting layer, etc.Examples of the material for the negative electrode include: alkalimetals such as Li, Na and K, and fluorides and oxides thereof; alkalineearth metals such as Mg and Ca, and fluorides and oxides thereof; gold;silver; lead; aluminum; alloys and mixtures of sodium and potassium;alloys and mixtures of lithium and aluminum; alloys and mixtures ofmagnesium and silver; rare earth metals such as indium and ytterbium;mixtures thereof; etc. The negative electrode is preferably made of amaterial having a work function of 4.0 eV or less, more preferably madeof aluminum, an alloy or a mixture of lithium and aluminum, or an alloyand a mixture of magnesium and silver.

The negative electrode may have a single-layer structure or amulti-layer structure. Preferred multi-layer structure isaluminum/lithium fluoride, aluminum/lithium oxide, etc. The negativeelectrode may be provided by an electron beam method, a sputteringmethod, a resistance heating vapor deposition method, a coating method,etc. A plurality of materials may be simultaneously deposited. Thenegative electrode of an alloy may be formed by simultaneouslydepositing a plurality of metals, or by depositing an alloy preparedbeforehand. Sheet resistance of the negative electrode is preferably afew hundred Ω/square or less. Although thickness of the negativeelectrode may be appropriately selected depending on the material usedtherefor, generally, the thickness is preferably 10 nm to 5 μm, morepreferably 50 nm to 1 μm, particularly preferably 100 nm to 1 μm.

(C) Hole-Injecting Layer and Hole-Transporting Layer

The hole-injecting material and the hole-transporting material used forthe hole-injecting layer and the hole-transporting layer are notparticularly limited if they have any function of: injecting the holesprovided from the positive electrode into the light-emitting layer;transporting the holes to the light-emitting layer; and blocking theelectrons provided from the negative electrode. Examples of thehole-injecting material and the hole-transporting material includecarbazole, triazole, oxazole, oxadiazole, imidazole, polyarylalkanes,pyrazoline, pyrazolone, phenylenediamine, arylaiines, amino-substitutedchalcone, styrylanthracene, fluorenone, hydrazone, stilbene, silazane,aromatic tertiary amine compounds, styrylamine compounds, aromaticdimethylidyne compounds, porphyrin compounds, polysilane compounds,poly(N-vinylcarbazole), aniline copolymers, electrically conductivepolymers and oligomers such as oligothiophenes and polythiophenes,organic silane compounds, carbon, the transition metal complex (1),derivatives and mixtures thereof, etc.

Each of the hole-injecting layer and the hole-transporting layer mayhave a structure of single-layer made of one or more materials, ormulti-layers made of the same material or different materials. Thehole-injecting layer and the hole-transporting layer may be formed by avacuum deposition method, an LB method, an ink-jet method, a printingmethod, a transferring method, a coating method using a solution or adispersion containing the above material such as a spin-coating method,a casting method and a dip-coating method, etc.

The solution and the dispersion used in the coating method may contain aresin. Examples of the resin include poly(vinyl chloride),polycarbonates, polystyrene, poly(methyl methacrylate), poly(butylmethacrylate), polyesters, polysulfones, poly(phenylene oxide),polybutadiene, poly(N-vinylcarbazole), hydrocarbon resins, ketoneresins, phenoxy resins, polyamides, ethyl cellulose, poly(vinylacetate), ABS resins, polyurethanes, melamine resins, unsaturatedpolyester resins, alkyd resins, epoxy resins, silicone resins, etc.Although the thickness of each of the hole-injecting layer and thehole-transporting layer is not particularly limited, generally, thethickness is preferably 1 nm to 5 μm, more preferably 5 nm to 1 μm,particularly preferably 10 to 500 nm.

(D) Light-Emitting Layer

In the light-emitting layer, holes injected from the positive electrode,the hole-injecting layer or the hole-transporting layer and electronsinjected from the negative electrode, the electron-injecting layer orthe electron-transporting layer are recombined to emit light when anelectric field is applied to the light-emitting device. A light-emittingmaterial for the light-emitting layer is not particularly limited ifonly they have functions of: receiving the holes provided from thepositive electrode, etc.; receiving the electrons provided from thenegative electrode, etc.; transporting the charges; and providing theoccasion where the holes and the electrons are recombined to emit lightwhen an electric field is applied to the light-emitting device. Thelight-emitting material may be such that utilizes singlet exciton,triplet exciton or both thereof for light emission, and examples thereofinclude: benzoxazole; benzoimidazole; benzothiazole; styrylbenzene;polyphenyl; diphenyl butadiene; tetraphenylbutadiene; naphthalimide;coumarin; perylene; perynone; oxadiazole; aldazine; pyralidine;cyclopentadiene; bis(styryl)anthracene; quinacridone; pyrrolopyridine;thiadiazolopyridine; cyclopentadiene; styrylamine; aromaticdimethylidine compounds; metal complexes such as 8-quinolinol metalcomplexes, rare-earth metal complexes and transition metal complexes;high molecular weight light-emitting material such as polythiophene,polyphenylene and polyphenylenevinylene; organic silane compounds; thetransition metal complex (1); derivatives thereof; etc.

The light-emitting layer may be made of one material or a plurality ofmaterials. The light-emitting device according to the present inventionmay comprise one light-emitting layer or a plurality of light-emittinglayers. Each of the light-emitting layers may emit light with adifferent color, to provide white light. The single light-emitting layermay provide white light. In the case where the light-emitting devicecomprises a plurality of light-emitting layers, each layer may be madeof one material or a plurality of materials.

The light-emitting layer may be formed by: a resistance heating vapordeposition method; an electron beam method; a sputtering method; amolecular stacking method; a coating method such as a spin-coatingmethod, a casting method and a dip-coating method; an ink-jet method; aprinting method; an LB method; a transferring method; etc. Among themethods, the resistance heating vapor deposition method and the coatingmethod are preferred. Although thickness of the light-emitting layer isnot particularly limited, generally, the thickness is preferably 1 nm to5 μm, more preferably 5 nm to 1 μm, particularly preferably 10 to 500nm.

(E) Electron-Injecting Layer and Electron-Transporting Layer

The electron-injecting material and the electron-transporting materialused for the electron-injecting layer and the electron-transportinglayer are not particularly limited if they have any function of:injecting the electrons provided from the negative electrode into thelight-emitting layer; transporting the electrons to the light-emittinglayer; and blocking the holes provided from the positive electrode.Examples of the electron-injecting material and theelectron-transporting material include: triazole; oxazole; oxadiazole;imidazole; fluorenone; anthraquinodimethane; anthrone; diphenylquinone;thiopyran dioxide; carbodimide; fluorenylidenemethane; distyrylpyrazine;anhydrides derived from a tetracarboxylic acid having such a aromaticring as a naphthalene ring and a perylene ring; phthalocyanine; metalcomplexes such as 8-quinolinol metal complexes, metallophthalocyanines,and metal complexes containing a benzoxazole ligand or a benzothiazoleligand; organic silane compounds; the transition metal complex (1);derivatives thereof; etc.

Each of the electron-injecting layer and the electron-transporting layermay have a structure of single-layer made of one or more materials, ormulti-layers made of the same material or different materials. Theelectron-injecting layer and the electron-transporting layer may beformed by a vacuum deposition method, an LB method, an ink-jet method, aprinting method, a transferring method, a coating method using asolution or a dispersion containing the above material such as aspin-coating method, a casting method and a dip-coating method, etc. Thesolution and the dispersion used in the coating method may contain aresin. Examples of the resin may be the same as those for thehole-injecting layer and the hole-transporting layer. Although thicknessof each of the electron-injecting layer and the electron-transportinglayer is not particularly limited, generally, the thickness ispreferably 1 nm to 5 μm, more preferably 5 nm to 1 μm, particularlypreferably 10 to 500 nm.

(F) Protective Layer

The protective layer acts to shield the light-emitting device frompenetration of moisture, oxygen, etc. that promotes deterioration of thedevice. Examples of a material for the protective layer include: metalssuch as In, Sn, Pb, Au, Cu, Ag, Al, Ti and Ni; metal oxides such as MgO,SiO, SiO₂, Al₂O₃, GeO, NiO, CaO, BaO, Fe₂O₃, Y₂O₃ and TiO₂; metalfluorides such as MgF₂, LiF, AlF₃ and CaF₂; nitrides such as SiN andSiN_(x)O_(y); polyethylene; polypropylene; poly(methylmethacrylate);polyimides; polyureas; polytetrafluoroethylene;polychlorotrifluoroethylene; polydichlorodifluoroethylene; copolymers ofchlorotrifluoroethylene and dichlorodifluoroethylene; copolymers oftetrafluoroethylene and at least one comonomer; fluorine-containingcopolymers having a cyclic structure in the main chain; amoisture-absorbing substance having a water absorption of 1% or more; amoisture-resistant substance having a water absorption of 0.1% or less;etc.

The protective layer may be formed by a vacuum deposition method, asputtering method, an activated sputtering method, a molecular beamepitaxy method (MBE method), a cluster ion beam method, an ion-platingmethod, a plasma polymerization method, a high frequency excitationion-plating method, a plasma CVD method, a laser CVD method, a thermalCVD method, a gas source CVD method, a coating method, an ink-jetmethod, a printing method, a transferring method, etc.

EXAMPLES

The present invention will be explained in further detail by thefollowing Examples without intention of restricting the scope of thepresent invention defined by the claims attached hereto.

Synthesis Example 1

Synthesis of Transition Metal Complex (1-20)

To a solution prepared by adding 20 ml of chloroform to 0.08 g of apyridylazole derivative 2 was added 0.08 ml of a methanol solution ofCH₃ONa (28 weight %) dropwise, and the resulting solution was stirred atroom temperature for 10 minutes. To this solution was added 0.2 g of aniridium complex 1, and the resultant was stirred at the room temperaturefor 3 hours. The iridium complex 1 may be prepared by a method describedin J. Am. Chem. Soc., 1984, 106, 6647. Then, to this were added 50 ml ofchloroform and 50 ml of water, and an organic phase and a water phasewere separated. The organic phase was dried with sodium sulfate,concentrated and recrystallized from chloroform/methanol, to provide 0.1g of the transition metal complex (1-20) as a yellow solid. Structure ofthe product was confirmed by MS spectrum (FAB-MASS spectrum (posi)=695).Thus-obtained transition metal complex (1-20) had a melting point of 220to 223° C.

Synthesis Example 2

Synthesis of Transition Metal Complex (1-203)

To 11.8 ml of 2-acetylpyridine was added 100 ml of ethanol, and furtheradded 15 g of trifluoroacetoacetic ester. The resulting solution wasadded 22.4 ml of a methanol solution of MeONa (28 weight %) dropwise to,stirred under reflux for 2 hours, and cooled to the room temperature. Tothe resulting solution was added 300 ml of ethyl acetate and 300 ml ofwater, and further added 1 mol/l hydrochloric acid aqueous solution suchthat water phase exhibited pH of approximately 7. Then, organic phasewas separated, washed with 100 ml of water and 100 ml of saturatedsodium chloride solution, dried with sodium sulfate and concentrated.Residue was purified by column chromatography (chloroform) to provide abrown liquid. This liquid was dissolved in 50 ml of ethanol, added 7.8 gof hydrazine hydrate to, stirred under reflux for 3 hours, and cooled tothe room temperature. To this were added 200 ml of ethyl acetate and 200ml of water and organic phase and water phase were separated. Theorganic phase was washed with 100 ml of water and 100 ml of saturatedsodium chloride solution, dried with sodium sulfate and concentrated.Residue was purified by column chromatography (chloroform) to provide 5g of compound 4 as a white solid.

To 0.2 g of compound 3 and 0.1 g of the compound 4 was added 20 ml ofchloroform. The resulting solution was added 0.09 ml of a methanolsolution of MeONa (28 weight %) dropwise to, stirred under reflux for 3hours, and cooled to the room temperature. To this were added 50 ml ofchloroform and 50 ml of water and organic phase were separated.Thus-obtained organic phase was dried with sodium sulfate andconcentrated. Residue was purified by column chromatography(chloroform), recrystallized from chloroform/methanol, to provide 0.15 gof the transition metal complex (1-203) as a yellow solid. Structure ofthe product was confirmed by MS spectrum.

Synthesis Example 3

Synthesis of Transition Metal Complex (1-262)

4.2 g of 2-aminomethylpyridine was dissolved in 100 ml of acetonitrile,and to this was added 9.8 ml of trifluoroacetic anhydride dropwise. Theresultant solution was stirred at the room temperature for 1 hour, and400 ml of ethyl acetate and 400 ml of water was added thereto. Tothus-obtained solution was added sodium hydrogen carbonate stepwiseuntil foaming was not observed, and organic phase were separated andconcentrated to provide 4 g of compound 5 as a brown solid.

To 0.5 g of the compound 3 and 0.23 g of the compound 5 was added 20 mlof chloroform. The resulting solution was added 0.22 ml of a methanolsolution of MeONa (28 weight %) dropwise to, stirred under reflux for 1hour, and cooled to the room temperature. To this were added 50 ml ofethyl acetate and 50 ml of water, and organic phase was separated.Thus-obtained organic phase was dried with sodium sulfate andconcentrated. Residue was purified by column chromatography (chloroform)to provide 0.35 g of the transition metal complex (1-262) as a yellowsolid. Structure of the product was confirmed by MS spectrum.

Synthesis Example 4

Synthesis of Transition Metal Complex (1-228)

To 10.6 ml of ethyl picolinate was added 100 ml of tetrahydrofuran, andto this was added 4.1 g of acetone. The resulting solution was added 27ml of a methanol solution of MeONa (28 weight %) dropwise to, stirredunder reflux for 3 hours, and cooled to the room temperature. To thiswere added 300 ml of ethyl acetate and 300 ml of water, and furtheradded 1 mol/l hydrochloric acid aqueous solution such that water phaseexhibited pH of approximately 7. Then, organic phase were separated,washed with 100 ml of water and 100 ml of saturated sodium chloridesolution, dried with sodium sulfate and concentrated. Residue waspurified by column chromatography (chloroform) to provide a brownliquid. This liquid was dissolved in 50 ml of ethanol, added 7 g ofhydrazine hydrate to, stirred under reflux for 2 hours, and cooled tothe room temperature. To this were added 200 ml of ethyl acetate and 200ml of water and organic phase and was separated. The organic phase waswashed with 100 ml of water and 100 ml of saturated sodium chloridesolution, dried with sodium sulfate and concentrated. Residue wassubjected to crystallization using hexane/chloroform, to provide 8 g ofcompound 6 as a waxy solid.

To 0.18 g of the compound 6 were added 10 ml of methoxyethanol and 10 mlof water, and 0.13 g of t-C₄H₉OK was added thereto and stirred at theroom temperature for 10 minutes. 0.1 g of K₃IrCl₆ was added to theresulting solution, stirred under reflux for 4 hours, and cooled to theroom temperature. To this were added 50 ml of chloroform and 50 ml ofwater, and organic phase were separated. Thus-obtained organic phase wasdried with sodium sulfate and concentrated. Residue was purified bysilica gel column chromatography (chloroform/methanol=10/1) to provide0.05 g of the transition metal complex (1-228) as a yellow solid.Structure of the product was confirmed by MS spectrum.

Synthesis Example 5

Synthesis of Transition Metal Complex (1-343)

To 10 g of 2-cyanopyridine was added 30 ml of methanol and then added19.5 ml of a methanol solution of CH₃ONa (28 weight %), and theresulting solution was stirred at the room temperature for 1 hour. 5.5ml of acetic acid was added to the solution dropwise and stirred for 5minutes, and 17 g of trifluoroacetohydrazide was added thereto andstirred at the room temperature for 1 hour to precipitate a crystal. Thecrystal was separated by filtration, to this was added 50 ml of toluene,and the resulting mixture was stirred under reflux for 3 hours. Themixture was then cooled to the room temperature and the solvent wasremoved to 8.8 g of compound 7.

To 0.2 g of the compound 3and 0.12 g of the compound 7was added 20 ml ofchloroform. The resulting solution was added 0.11 ml of a methanolsolution of MeONa (28 weight %) dropwise to, stirred under reflux for 3hours, and cooled to the room temperature. To this were added 50 ml ofchloroform and 50 ml of water, and organic phase was separated.Thus-obtained organic phase was dried with sodium sulfate andconcentrated. Residue was purified by silica gel column chromatography(chloroform), and recrystallized from chloroform/methanol, to provide0.13 g of the transition metal complex (1-343) as a yellow solid.Structure of the product was confirmed by MS spectrum.

Example 1

1 mg of the transition metal complex (1-20), 40 mg ofpoly(N-vinylcarbazole) and 12 mg of2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD) were dissolvedin 2.5 ml of dichloroethane, and the obtained solution was applied to awashed ITO substrate by spin-coating (1500 rpm, 20 sec) to form anorganic layer having thickness of 98 nm. Then, on the organic layer wasdisposed a mask patterned for desired light-emitting area of 4 mm×5 mm,magnesium and silver (mole ratio: magnesium/silver=10/1) wasco-deposited on the organic layer into 50 nm in a deposition apparatus,and silver was further deposited thereon into 50 nm, to produce alight-emitting device of Example 1.

Thus-obtained light-emitting device was made to emit light whileapplying direct current voltage thereto by “Source-Measure Unit 2400”manufactured by TOYO CORPORATION, and measured with respect to luminanceby “Luminance Meter BM-8” manufactured by TOPCON CORPORATION. Thelight-emitting device of Example 1 emitted a green light and exhibitedmaximum luminance of 6800 cd/m² and minimum driving voltage of 9 V.Incidentally, in this invention, the “minimum driving voltage” means aminimum valve of driving voltage required by the light-emitting deviceto emit light. Further, the light-emitting device of Example 1 was leftto stand in the air for 1 day, and then, the luminance was measuredagain to evaluate its durability. As a result, the light-emitting deviceof Example 1 exhibited the maximum luminance of 5900 cd/m².

Example 2

A light-emitting device of Example 2 was produced and evaluated withrespect to the luminance and the durability in the same manner asExample 1 except for using the transition metal complex (1-22) insteadof the transition metal complex (1-20). As a result, the light-emittingdevice of Example 2 emitted a green light and exhibited the maximumluminance of 3700 cd/m² and the minimum driving voltage of 9 V. Further,the light-emitting device of Example 2 exhibited the maximum luminanceof 2700 cd/m² after the device was left to stand in the air for 1 day.

Example 3

A light-emitting device of Example 3 was produced and evaluated withrespect to the luminance and the durability in the same manner asExample 1 except for using the transition metal complex (1-1) instead ofthe transition metal complex (1-20). As a result, the light-emittingdevice of Example 3 emitted a bluish green light and exhibited themaximum luminance of 3400 cd/m² and the minimum driving voltage of 9 V.Further, the light-emitting device of Example 3 exhibited the maximumluminance of 3000 cd/m² after the device was left to stand in the airfor 1 day.

Comparative Example 1

A light emitting device of Comparative Example 1 was produced andevaluated with respect to the luminance and the durability in the samemanner as Example 1 except for using the following compound A instead ofthe transition metal complex (1-20). As a result, the light-emittingdevice of Comparative Example 1 emitted a green light and exhibited themaximum luminance of 3300 cd/m² and the minimum driving voltage of 11 V.Further, the light-emitting device of Comparative Example 1 exhibitedthe maximum luminance of 410 cd/m² after the device was left to stand inthe air for 1 day.

Comparative Example 2

A washed ITO substrate was placed in a deposition apparatus,N,N′-diphenyl-N,N′-di(m-tolyl)benzidine (TPD) was deposited on the ITOsubstrate into a thickness of 50 nm, the compound A and the followingcompound B (weight ratio: compound A/compound B=1/17) were co-depositedthereon into 36 nm, and further, thereon was deposited the followingazole compound C into 36 nm. On thus-obtained organic layer was disposeda mask patterned for desired light-emitting area of 4 mm×5 mm, lithiumfluoride was deposited on the organic layer into 3 nm in a depositionapparatus, and aluminum was further deposited thereon into 60 nm, toproduce a light-emitting device of Comparative Example 2.

Thus-obtained light-emitting device was made to emit light whileapplying direct current voltage thereto by “Source-Measure Unit 2400”manufactured by TOYO CORPORATION, and measured with respect to luminanceand emission wavelength. The luminance was measured by “Luminance MeterBM-8” manufactured by TOPCON CORPORATION and the emission wavelength wasmeasured by “Spectral Analyzer PMA-11 ” manufactured by HamamatsuPhotonics K.K. As a result, the light-emitting device of ComparativeExample 2 emitted a green light with EL_(max) of 518 nm and chromaticityof (0.31, 0.61), and exhibited external quantum efficiency of 7.2%.Incidentally, the external quantum efficiency was obtained by theluminance, emission spectrum, current density and luminosity curve.

Example 4

A light-emitting device of Example 4 was produced and evaluated withrespect to the luminance and the external quantum efficiency(light-emitting efficiency) in the same manner as Comparative Example 2except for using the transition metal complex (1-201) instead of thecompound A. As a result, the light-emitting device of Example 4 emitteda blue light with EL_(max) of 470 nm and chromaticity of (0.16, 0.34),and exhibited external quantum efficiency of 8.0%.

Example 5

A light-emitting device of Example 5 was produced and evaluated withrespect to the luminance and the external quantum efficiency in the samemanner as Comparative Example 2 except for using the transition metalcomplex (1-203) instead of the compound A. As a result, thelight-emitting device of Example 5 emitted a blue light with EL_(max) of463 nm and chromaticity of (0.17, 0.28), and exhibited external quantumefficiency of 8.0%.

Example 6

A light-emitting device of Example 6 was produced and evaluated withrespect to the luminance and the external quantum efficiency in the samemanner as Comparative Example 2 except for using the transition metalcomplex (1-262) instead of the compound A. As a result, thelight-emitting device of Example 6 emitted a blue light with EL_(max) of469 nm and chromaticity of (0.17, 0.36), and exhibited external quantumefficiency of 7.0%.

Example 7

A washed ITO substrate was placed in a deposition apparatus,N,N′-diphenyl-N,N′-di(m-tolyl)benzidine (TPD) was deposited on the ITOsubstrate into a thickness of 50 nm, the following compound D and thefollowing compound E (weight ratio: compound D/compound E=1/17) wereco-deposited thereon into 18 nm, the transition metal complex (1-203)and the compound B (weight ratio: transition metal complex(1-203)/compound B=1/17) were co-deposited thereon into 18 nm, andfurther, thereon was deposited the azole compound C into 36 nm. Onthus-obtained organic layer was disposed a mask patterned for desiredlight-emitting area of 4 mm×5 mm, lithium fluoride was deposited on theorganic layer into 3 nm in a deposition apparatus, and aluminum wasfurther deposited thereon into 60 nm, to produce a light-emitting deviceof Example 7. The light-emitting device of Example 7 was evaluated withrespect to the luminance and the external quantum efficiency in the samemanner as Comparative Example 2. As a result, the light-emitting deviceof Example 7 emitted a white light with chromaticity of (0.33, 0.30),and exhibited external quantum efficiency of 8.1%.

Example 8

A light-emitting device of Example 8 was produced and evaluated withrespect to the luminance and the external quantum efficiency in the samemanner as Comparative Example 2 except that the transition metal complex(1-208) was used instead of the compound A and that the transition metalcomplex (1-208) and the compound B was co-deposited at weight ratio oftransition metal complex (1-208)/compound B=2/17. As a result, thelight-emitting device of Example 8 emitted a blue light with EL_(max) of462 nm and chromaticity of (0.15, 0.29), and exhibited external quantumefficiency of 6.5%.

Example 9

A light-emitting device of Example 9 was produced and evaluated withrespect to the luminance and the external quantum efficiency in the samemanner as Comparative Example 2 except that the transition metal complex(1-209) was used instead of the compound A and that the transition metalcomplex (1-209) and the compound B was co-deposited at weight ratio oftransition metal complex (1-209)/compound B=2/17. As a result, thelight-emitting device of Example 9 emitted a blue light with EL_(max) of456 nm and chromaticity of (0.15, 0.24), and exhibited external quantumefficiency of 3.2%.

Example 10

A light-emitting device of Example 10 was produced and evaluated withrespect to the luminance and the external quantum efficiency in the samemanner as Comparative Example 2 except that the transition metal complex(1-343) was used instead of the compound A and that the transition metalcomplex (1-343) and the compound B was co-deposited at weight ratio oftransition metal complex (1-343)/compound B=2/17. As a result, thelight-emitting device of Example 10 emitted a blue light with EL_(max)of 462 nm and chromaticity of (0.15, 0.29), and exhibited externalquantum efficiency of 8.1%.

Example 11

A light-emitting device of Example 11 was produced and evaluated withrespect to the luminance and the external quantum efficiency in the samemanner as Comparative Example 2 except that the transition metal complex(1-344) was used instead of the compound A and that the transition metalcomplex (1-344) and the compound B was co-deposited at weight ratio oftransition metal complex (1-344)/compound B=2/17. As a result, thelight-emitting device of Example 11 emitted a blue light with EL_(max)of 453 nm and chromaticity of (0.15, 0.21), and exhibited externalquantum efficiency of 1.3%.

Example 12

A light-emitting device of Example 12 was produced and evaluated withrespect to the luminance and the external quantum efficiency in the samemanner as Comparative Example 2 except that the transition metal complex(1-360) was used instead of the compound A and that the transition metalcomplex (1-360) and the compound B was co-deposited at weight ratio oftransition metal complex (1-360)/compound B=2/17. As a result, thelight-emitting device of Example 12 emitted a blue light with EL_(max)of 453 nm and chromaticity of (0.15, 0.27), and exhibited externalquantum efficiency of 5.1%.

Example 13

A light-emitting device of Example 13 was produced and evaluated withrespect to the luminance and the external quantum efficiency in the samemanner as Comparative Example 2 except for using the transition metalcomplex (1-352) instead of the compound A. As a result, thelight-emitting device of Example 13 emitted a blue light.

Example 14

A light-emitting device of Example 14 was produced and evaluated withrespect to the luminance and the external quantum efficiency in the samemanner as Comparative Example 2 except for using the transition metalcomplex (1-228) instead of the compound A. As a result, thelight-emitting device of Example 14 emitted a bluish green light.

As described in detail above, the light-emitting device of the presentinvention using the transition metal complex (1) can emit a light ofblue, white, etc. with high luminance and light-emitting efficiency, andexhibits low minimum driving voltage and excellent durability. In thisinvention, a blue light-emitting device having a small chromaticitydifference and high light-emitting efficiency can be obtained by usingthe transition metal complex (1). Thus, the light-emitting deviceaccording to the present invention can be preferably used for indicatingelements, display devices, backlights, electro-photographies,illumination light sources, recording light sources, exposing lightsources, reading light sources, road signs or markings, signboards,interiors, optical communications, etc. The transition metal complex (1)is usable for the light-emitting device and has a wide applicability formedical treatments, fluorescent whitening agents, photographicmaterials, UV-absorbing materials, laser dyes, dyes for color filters,color conversion filters, etc.

1. A light-emitting device comprising a pair of electrodes and one ormore organic layers disposed between said electrodes, said one or moreorganic layers comprising a light-emitting layer, wherein at least oneof said one or more organic layers comprises a transition metal complexcontaining a moiety represented by the following formula (8):

wherein M⁸¹ is a metal ion selected from the group consisting ofruthenium, rhodium, tungsten, rhenium, osmium, iridium and platinum; Q⁸¹represents an atomic group forming a nitrogen-containing heterocyclicring; and R⁸¹ and R⁸² represent a hydrogen atom or an alkyl, alkenyl oralkoxy group, respectively.
 2. The light-emitting device of claim 1,wherein M⁸¹ is a metal ion selected from the group consisting ofruthenium, rhenium, iridium and platinum.
 3. The light-emitting deviceof claim 2, wherein M⁸¹ is iridium.
 4. The light-emitting device ofclaim 1, wherein the maximum emission wavelength of the transition metalcomplex containing a moiety represented by the formula (8) is from 380to 500 nm.
 5. The light-emitting device of claim 1, wherein thetransition metal complex containing a moiety represented by the formula(8) serves as a light-emitting material or an electron-transportingmaterial.
 6. The light-emitting device of claim 5, wherein thetransition metal complex containing a moiety represented by the formula(8) serves as a light-emitting material.
 7. The light-emitting device ofclaim 1, wherein the at least one of said one or more organic layersfurther comprises a host compound.